Excuse me if I come over all incoherent, but I don't have the terminology for what I mean...
On another forum I'm on, there is a button that takes you to the last post you saw on a thread before logging out. At the minute, if I leave a thread with 8 pages and it has 23 when I log back on, unless I have specifically remembered the number of pages/date and time of the last post I looked at (NOT likely...) then I have to trawl about trying to find where I left off.
Does this function exist somewhere really obvious and I'm being a peabrain?